It is known to provide hand held brake pad spreader tools having disc a retractable piston. Retraction of the piston can be pneumatic via a threaded shaft that when utilised pushes the piston back into its bore (see for example. Blake U.S. Pat. No. 6,195,863 or Markous U.S. Pat. No. 5,018,261). These tools are either expensive or extremely slow.
A further example of what is termed a brake pad spreading tool has a pair of plates which are offset from the operating mechanism and which are pushed apart by a hydraulic mechanism (see for example Ratchovsky U.S. Pat. No. 6,378,185). If the piston has much resistance (caused by dry seals, corrosion or foreign matter), the plates will deform and exert uneven pressure on the piston face causing further resistance.
Another example is shown in Miller U.S. Pat. No. 7,155,792 which uses a toothed rod and a hand operated ratchet mechanism in a similar way to the mastic gun of Kelsey GB 782365. The hand tool of U.S. Pat. No. 7,155,792 consists of a shaft having a ram affixed onto a front end that slidably extends through a central aperture in a frame member and a central through bore in a backing plate that is mounted to a forward end of the frame member. A trigger handle is pivotally affixed to the frame member adjacent to a depending fixed handle on the frame member. A mechanism is for moving the shaft forwards when the trigger handle is squeezed towards the fixed handle by a hand of a person. A mechanism is for holding the shaft stationary thereby preventing the shaft from moving backwards when the trigger handle is released. Such tools work on the face of the caliper piston which can result in the piston seal being destructively pinched between the caliper housing and the tool “ram” as the piston is fully retracted.
In general, rear brake calipers incorporating “hand brake” type mechanisms have wind forward type mechanisms to allow for the wear of the material of the disc pad. These need to be wound back to allow for insertion of fresh disc pads having greater thickness of the material. These wind back mechanisms have either clockwise or anti-clockwise threads and the tools required to operate them are of two separate types; clockwise or anti-clockwise thread types.
It is recognised that a superior tool which can be used on several sizes and types of caliper piston and which is less expensive to manufacture is desired.